Kirk enters the turbolift wearing his regular gold uniform, but exits onto the bridge wearing his little green wrap-around top with the shiny trim.

Spock and McCoy have a brief argument over whether Charlie could have survived on his own all those years. Because they're talking at the same time, Spock saying "Doctor" as McCoy says "Mr. Spock," the closed captioner apparently misunderstood McCoy's line. The caption has him calling Spock "Dr. Spock."

The Enemy Within

Granted that "Star Trek" used a very broad definition of sentient with regard to other life forms, but the alien dog in this episode was definitely referred to as an animal, and demonstrated no indication of intelligence. In which case, McCoy should have referred to its post-mortem exam not as an autopsy, but as a necropsy. Autopsies are only performed on people, or in the ST universe, on intelligent life forms.
 

What Are Little Girls Made Of?

When Dr. Korby's androids place the mummy-like "blank" on the machine to create the android duplicate of Kirk, its physical proportions are a bit off. The blank appears human-shaped in every aspect except for its legs, which are truncated just below the knees. The blank grows legs and feet anyway and becomes the android Kirk. But why the short legs on the prop dummy? Did they run out of plaster?

City on the Edge of Forever

In 1930, Edith Keeler thinks it's strange that Dr. McCoy has never heard of Clark Gable. What's strange is that she has. Gable was an unknown bit player until 1932.

While he and Kirk discuss the history tapes in their room, Spock's shirt collar is turned up on the left side in close-ups, but straightened out in the full shots.

After Edith stumbles and nearly falls down the stairs, she still has both her shoes on. But after the kiss, she proceeds up the stairs and is now carrying one shoe. She had no time to take it off, as she was, er, busy with Kirk the whole time.

Galileo 7

Here, as in a number of other episodes, characters are beamed onto the Enterprise from (originally) a sitting position, as the 5 surviving Galileo crew are at the end of this one. Was the transporter smart enough to reconfigure them standing up, or perhaps to bring their chairs along so they wouldn't fall on their tushies as soon as they materialized?

It shouldn't have been necessary to send a fragile shuttlecraft out to investigate Murasaki 312 in the first place, particularly knowing that the "quasar-like formation" was "ionizing the entire sector" and messing up sensors and communications, not to mention transporters. Surely the phenomenon could have been studied far more efficiently from the Enterprise itself?

Squire of Gothos

Trelaine is very proud of his dueling pistols ("like the pair that slew your heroic Alexander Hamilton"). But he shouldn't even know who Hamilton was. He's been observing Earth 900 years ago, which, subtracting from ST's 23rd Century, means the 14th Century - the 1300s. Nearly everything in Trelaine's castle is from a much later period, including the harpsichord and the music played on it, the costumes, the furniture, and those pistols.

At the end, Kirk and Spock both use the term "mischevious." Though a common mispronunciation, that's not a word. It's mischievous, and it has 3 syllables, not 4. Spock, if not Kirk, should have known this.

Kirk's references at the end to "dipping little girls' curls in inkwells" and "stealing apples from the neighbors' trees" are glaring anachronisms, even for 1967. It's unlikely that even the well-read Kirk would be familiar with those pranks in the 23rd Century. The scriptwriters just wanted to have Kirk play a little joke on Spock. Funny, but maybe they should have chosen something a bit more "current" than the 1920s/30s? The scriptwriter here was showing his age!
 
Shore Leave

When Spock beams down after calculating there was just enough energy left for him to do so, Sulu and Kirk watch him materialize, and Sulu says, "Someone beaming down from the bridge." From the bridge? Shouldn't he have said "from the ship"? No one ever beamed down directly from the bridge, but even if they could, how would Sulu know that's where they'd come from?

Don Juan tears Yeoman Barrows' tunic at the right shoulder. Near the end, when she changes from the fairy tale dress back into the tunic, the torn right shoulder is suddenly mended. They're cut off from the ship by the power drain, so she couldn't have beamed up for a new one. She emerges from the bushes after changing, and now her tunic is torn at the left shoulder.

Finnegan flips Kirk over his shoulder near the end of their fight. When Kirk lands, his uniform is still completely intact, but when we cut to a close-up, his shirt is suddenly shredded.

Near the end of the episode, the heavy chains restraining the "loose" tiger are visible both around his neck and running across the rocks to the right of the shot.

Corbomite Maneuver

As Balok's 10 minutes are counting down, McCoy comes onto the bridge wearing a standard blue velour uniform. A few minutes later, when Spock says he can bring up Balok's image, McCoy is suddenly wearing his medical tunic with the different fabric and collar. Then when Bailey starts losing it, McCoy is back in the regular velour costume again.

Throughout this episode, no one seems to agree on how Balok's name should be pronounced. Half the time, the actors pronounce it "Baylock." The rest of the time, it's pronounced "Balleck."

Miri

Leaving aside the extreme improbability that it could exist at all, why does the duplicate Earth have not a single cloud anywhere on the entire planet? Earth-like, and especially Earth-duplicate, planets have atmospheres; atmospheres create weather and weather creates clouds. "It's science fiction" neither excuses nor explains away the error. There are no clouds when there should be because the special effects crew forgot to put them in.

The dust smudging both Spock's uniform and that of the older security guard instantly vanishes when they leave the building to search for the onlies.

Trivia: Most of the onlies in the final scenes were the children of Star Trek's cast and crew. They included William Shatner's two young daughters, Leslie and Lisabeth Shatner.

Court Martial

McCoy uses a "masking device" to block out the bridge personnel's heartbeats (and apparently, they couldn't come up with a prop for this any better than an ordinary microphone). When McCoy masks Spock's heartbeat, he holds the microphone, err, masking device over the wrong part of Spock's anatomy. We'd already established that Spock's heart wasn't in the same place as a human's.

No reputable military court would have permitted Areel Shaw to either prosecute or defend Captain Kirk. Her previous romantic relationship with the defendant constitutes an egregious conflict of interest. If the authorities were unaware of this, she was still ethically and legally bound to recuse herself.

Space Seed

At the hearing in the final scene, there are two bits of debris of some sort (small, black and roundish) littering the floor at the bottom left of the screen. Whatever it was disappears when Scott, Spock, Kirk and McCoy get up to leave the room. Uhura also does an unintentional disappearing act here. We see her getting up from her small table just at the left edge of the screen, but unlike the people in Khan's party and the rest of the security personnel, we never see her cross in front of the camera and leave. She's just suddenly gone.

Devil in the Dark

When he's just determined that the creature's body secretes an extremely corrosive substance, why does Spock, with his bare hands and without scanning it first, pick up the piece of horta that fell off when it was shot?

Here, as in nearly every other ST episode featuring caves, caverns or mines, all the floors are perfectly flat and the lighting adequate-to-see-by or even brilliant. These configurations are easily found on soundstage sets - but not in nature.

How does the horta create all those perfectly round tunnels when the horta isn't round?

When they first arrive at the mining complex, Kirk asks Chief Vanderberg, "Did you post centuries?" He means sentries, of course, and the closed captioning corrected it to "sentries." But that's not what he says.

After his initial mind meld with the horta, Spock tells Kirk, "That's all I got, Captain: waves and waves of searing pain." A minute later, he says that it's "a highly intelligent, extremely sophisticated animal" that calls itself a horta. Apparently, waves of searing pain were not all that he got after all.

Arena

During the attack on the outpost, as Spock arrives in his foxhole, Kirk puts down the box of ammunition and positions the grenade launcher. We cut to a higher angle as Spock scrambles around to the Captain's left, and Kirk is putting the box down and positioning the launcher all over again. As the action was supposedly continuous, there wasn't time for Kirk to pick the items up and set them down a second time.

When the Metrons first allow the Enterprise to see what's happening on the surface, the landscape appears first - and then the Gorn fades into the shot a few seconds later. The fade-in effect makes no sense. Why would the Metrons need it? Why did we?

The giant rock sitting on the promontory, in long shot, is much larger than the Kirk stand-in stunt man who climbs the rock face to reach it. Next shot, when Kirk pushes the boulder over the edge, it's suddenly much smaller than he is. When it lands on the Gorn, the rock is even smaller - now less than half its original size.

When Kirk reappears on the bridge at the end, his uniform, dusty and dirty on the surface, is once again spotless and the smudges are instantly gone from his face.

Spock refers to diamonds here as the hardest known substance. In "Balance of Terror," he says that rodinium is the hardest known substance. In "Doomsday Machine," tritanium is given that honor, also by Spock.

Kirk's voice-over log entry says he's been "placed on the surface of an asteroid." The Metron's simply referred to it as a planet prepared for them with a suitable atmosphere. How and why does Kirk suddenly assume that it's an asteroid rather than a full sized planet?

Return of the Archons

In the exterior shot, the double front doors of Reger's house have large curtained windows in them. After the Enterprise landing party rushes inside and closes the doors, however, they're suddenly solid wood with no windows.

As Kirk and co. carries O'Neil out of the alley, the supposedly unconscious woman in the black dress moves her foot out of the way as they pass.

The lawgivers' robes that Kirk and Spock take off and drop on the floor just inside the doorway disappear after they phaser the wall to reveal Landru. The robes reappear a few minutes later, but have now migrated several feet to one side, bunched up against the wall where they are no longer in tripping range of the actors about to enter the scene.

A Taste of Armageddon

Just after the ship is first attacked, Scotty tells McCoy, "We can't fire full phasers with our screens up." Since when? The Enterprise couldn't operate transporters with the shields up, but it fired its phasers, full or otherwise, with the screens up every time it went into battle, and always had. If they'd been forced to shut their shields down every time they fired, the Enterprise would have been history long before this.

The Alternative Factor

Both the positive and negative versions of Lazarus have a long mustache and a fairly full "waterfall" beard - until the scene in the briefing room, when inexplicably, the mustache and beard are both suddenly so thin they're barely visible. As soon as they beam down to the planet, however, the much thicker facial hair is restored.

Mad Lazarus has just put a black-and-white hatch cover over the stolen dilithium crystal in his time ship. It's in place when Kirk arrives to confront him. But a moment later, when Kirk leans in and is accidentally transported to the negative universe, the cover has disappeared. It's still missing when Kirk returns to push Lazarus through the portal.

Kirk and co. know that Lazarus is insane and that he wants their dilithium crystals. Yet he's not restrained in sickbay and is, in fact, given free run of the ship so that he can knock out the crew in engineering and steal the crystals. Other than to further a woefully weak plotline, this makes no sense whatsoever.

 
Mudd's Women

Is there a 23rd Century equivalent of Terminix for spaceships? When Mudd offers Eve the Venus drug in her quarters aboard the Enterprise, a bug flits past the camera.
 

The Changeling

After Spock mind melds with Nomad, Kirk hustles him out into the corridor. In the shots taken from behind Kirk, the Captain's left hand is high on Spock's shoulder. In the reverse angles, his hand is several inches lower on Spock's arm.

When Nomad's bolt sends Scotty flying across the bridge, you can see the two rubber mats placed on the floor for the stunt man to land on.

Mirror, Mirror

When Kirk sits down to consult the computer, the big green potted plant on the shelf behind him is there in full shots and missing in close-ups. It's much too large to be completely hidden behind him: if it shows up behind his head in full shot, it should show in close-ups, too, but it doesn't. It's not there.

Who Mourns for Adonais?

Kyle reports the landing party's whereabouts on the surface, and Spock asks, "And Apollo?" Kirk had no chance to call the ship after Apollo revealed his name - so Spock should not have known it.

When Apollo first grows large, the shimmering edge of the special effects matte is visible in the sky just above his right shoulder.

Apollo's lightning bolt throws Scotty across the table and dislodges a big bunch of green grapes from the fruit bowl. They fall onto the table. But when Kirk's crew later assemble at the table, the green grapes aren't there, or in the bowl, or anywhere in the temple. They magically reappear in the bowl just after Spock gets through to Kirk on the communicator.

The fruit bowl disappears from the table altogether just before the Enterprise fires on the temple. The small statue that's been there from the start vanishes as well.

Spock says they've only managed to punch holes in the force field large enough to fire through. But when the Enterprise fires, the force field (in the shape of Apollo's hand) is no longer there at all.

 
Catspaw

When the giant cat breaks down the cell door, Korob falls beneath it face down with his head toward the door. In the very next shot, he's in a completely different position - face up with his feet toward the door.

 
Metamorphosis

The shiny gold blanket covering the dying Commissioner Hedford is tucked up to her neck in close-ups, but only reaches her upper waist in full shots.

 
The Deadly Years

The aging Kirk's hairline has receded considerably. When he ages still more and goes completely gray, however, the receding process inexplicably reverses itself, and he suddenly has much more hair on his forehead than before.

A Private Little War

The gash on Kirk's right cheek disappears between the time he and McCoy fall asleep in the cave and when McCoy wakes up to find Kirk at Nona's side.

When Nona is trying to seduce Kirk, we see a close-up of him with nothing on his shoulders. Cut to a two-shot and suddenly Nona's arms are over his shoulders and around his neck.

While Nona is struggling with her Villager attackers, the camera tilts just far enough to show, in the distance, a nice (if slightly smoggy) view of buildings, docks and boats in Santa Monica Harbor.
 
 
A Piece of the Action

In the very first scene after the intro, when Bela's goons hold the landing party at gunpoint, Spock's position on the sidewalk shifts back and forth from standing on the other side of a wooden bench to standing alongside Kirk and McCoy with no bench in between. In fact, in the latter shots, the bench has moved all the way across the street.

Kirk has just tripped both of Krako's goons with the radio wire strung across the door. He knocks them both out, grabs a gun and then races out the door - right through the space that should still be strung with the trip wire. Oops.

While Kirk and McCoy attack the other two henchmen, Spock shoulder-pinches the card-playing gangster. In the very next shot, Spock's position has jumped from behind the now-unconscious man to several feet away, where he is bending over to retrieve the guns from the floor.

Not only do the billiard balls on the pool table keep changing positions between shots, but Bela seems to forget what the cue ball is for, and starts hitting the colored balls directly into the pockets instead.

At the end of act one, the cue stick standing upright against the pool table just in front of Spock disappears when the view cuts to an overhead shot. It's back again after the commercial break.

 
The Gamesters of Triskelion

When Chekov's drill thrall sits down and nuzzles up to him in his cell, the boom shadow is visible on the wall at the upper left corner of the screen.

The Providers' representative colors on the game platform and the thralls' collars (all three colors are on Galt's collar) are red, yellow and blue. But when Kirk appears before them, the Providers themselves are red, yellow and green, and so is the gaming symbol inside their glass bubble.

At the end, the freed thralls, including Kirk, Chekov and Uhura, remove their collars and throw them onto the game platform. But when Kirk and his crew beam away, the collars have all disappeared.

 
The Trouble With Tribbles

The tribble-inundated Kirk is holding one of the small fur balls in both hands in some shots, but when the camera angle changes, that tribble vanishes and his hands are no longer even close together.

When Kirk is standing in the huge pile of tribbles, he's cradling two large tribbles in his arms in full shots, but only one, and in a different position, in close-ups.

 
Wolf in the Fold

In the briefing room, Hengist and the Prefect are sitting in chairs against the wall at least a foot apart, with bright overhead lighting that casts no shadows on the wall behind them. When we cut to a two-shot of them, however, they're suddenly shoulder-to-shoulder with almost no space between them, and the lighting changes to cast very dark shadows behind them.

 
Obsession

At the end, when Kirk and Garrovick are beamed up seconds before the explosion, Kirk is holding his communicator up to his mouth with both hands. But when they finally materialize on the Enterprise, Kirk's hands are down at his sides: no communicator in sight.

 
Friday's Child

Kirk's arrow strikes the Klingon in the knee. But a few shots later, the shaft is protruding from his thigh, several inches above its original position. Still later, he's holding one hand to his calf just *below* the knee, which isn't where the arrow was either time.

When the Klingon shoots Maab with a hand phaser, the beam is yellow as he fires, but red when it strikes Maab.

Before the Capellans reach him, the Klingon's body moves into a completely different position, and to a different spot on the ground, than it was in when he first fell.

 
The Ultimate Computer

When M-5 destroys the ore freighter, Dr. Daystrom says, "Fortunately, it was only a robot ship." But Daystrom wasn't on the bridge yet when Spock announced that fact. He didn't have any way to know that the freighter was unmanned.
 

Assignment: Earth

Scotty is receiving images of the launch, supposedly from an orbiting satellite. But many of the camera views are obviously from ground level, and couldn't possibly have been taken from orbit.

Isis the cat was disinclined to hold still for special effects shots. When Gary Seven beams off the Enterprise with the cat in his arms, the position of her head jumps several inches as they're dematerializing.

When Isis meows and enters the inner office, the door is open several inches and the lights inside the room are on. When Gary Seven follows her in a few moments later, the door has nearly closed itself and the lights inside are off.

Gary Seven detonates the nuclear warhead 104 miles above the Earth. The world is saved and all is well. Only it wouldn't be. A nuclear explosion 100 miles up would not only short out everything electronic located below it, it would create deadly radiation fallout over a very wide area, and the world war he was trying to avert would probably still have occurred.
 

Bread and Circuses

The sword Spock is carrying disappears between leaving the cell and the group exiting down the corridor. No one else in the shot appears to have taken possession of it.
 

Spock's Brain

Trek's new 3rd season uniforms were tighter-fitting than their velour predecessors, presenting a problem for some actors. When the landing party beams down in this episode, the outline of William Shatner's tummy-wrapping girdle is very visibly showing through his costume.
 

The Paradise Syndrome

When Miramanee and her companion first see Kirk at the obelisk, the two women are standing, holding their fruit baskets, just inches from each other. In the very next, reverse angle shot, they're suddenly several feet apart.

On this planet that supposedly closely parallels Earth development, the primitive natives haven't yet discovered oil lamps, zippers or artificial respiration techniques. But they do have stretchy elastic/spandex headbands.
 

 Is There in Truth No Beauty?

The Enterprise takes a short, accidental trip outside the galaxy and can't find its way back without Kollos' help. But even at warp 9, the Big E would have to travel for months to get so far outside the Milky Way that they couldn't, well, just turn around and *see* it. Our galaxy is huge. 100,000 light years across. Very huge. Visible with the naked eye from 2 million light years away. Very very huge. And did we mention that it's huge? Oh, and don't assume that the energy barrier kept them from seeing home. Even that was enormous, pink(!), and visible.

When Kirk turns to follow Miranda across the arboretum, the camera shadow is briefly visible on the wall at the lower left of the screen.

The colorful nebulae of the energy barrier are showing through the hull of the suddenly-transparent Enterprise as it heads back into the galaxy.

In the sickbay scene near the end, someone got their line wrong, resulting in this contradictory bit of dialogue: Kirk: "He'll die. But that's what you want, isn't it?" Miranda: "That's a lie!" Kirk: "Oh yes it is - you want him to die." Miranda's line was supposed to be, "That's not true."

During the fight in engineering, Marvick's kick, throwing one of the engineering crewmen violently back against the wall, misses by an obvious mile.
 

Day of the Dove

In the opening scenes, Sulu's retractable viewer isn't there when the Klingon ship approaches on the view screen. But a moment later in a closer shot, the viewer is suddenly in front of him, fully extended.

When they first spot the alien in the ship's corridor, Kirk says that if they can't cease hostilities, "We're a doomed ship, traveling forever between galaxies." This was the only time original "Trek" ever committed the major scientific blunder (common in too many sci-fi shows) of confusing galaxies and solar systems. The Enterprise wasn't capable of intergalactic travel.
 
 
For the World is Hollow and I Have Touched the Sky

Kirk calls Scott to beam up, and lowers the communicator from his face as he looks at McCoy. In the next shot, he's holding it to his mouth once more. The shot changes one more time, and it's lowered again.

After he falls unconscious onto the blue rug, McCoy's position relative to the rug's top edge keeps changing between shots.

Natira orders the landing party to kneel before the oracle. Spock does so about a foot-and-a-half to McCoy's left. As the shots change, Spock "jumps" to McCoy's immediate side, then back to his original position, etc.
 
 
Spectre of the Gun

When Chekov sits outside the general store chatting with Sylvia, his left arm and her right alternate from entwined to un-entwined and back again as the shots change.
 
 
And the Children Shall Lead

In the final scene, Kirk asks Spock to play back the chant the children used "to summon the Gorgon." Neither the children nor the evil angel himself have, anywhere in the episode, used the term "Gorgon." Kirk just seems to divine the creature's name (exactly as it's designated in the script, amazingly enough) out of thin air.
 
 
Whom Gods Destroy

When Garth forces Kirk to kneel at his feet, Kirk's hands are extended palms down, then palms up, then palms down again as the camera angles change.

As Garth forces Kirk to watch the governor tortured, the pedestal fruit bowl in front of Kirk keeps moving back and forth in relation to the pitcher.

When Marta kisses Kirk, her hands leave green make-up smeared all over the left shoulder and back of his uniform tunic.

At the end, Kirk teases Spock about letting himself be hit on the head in order to determine which Kirk was genuine. But the phony Kirk never hit Spock on the head. He merely pushed Spock over and attacked the real Kirk.